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Summary: The interaction potential of a symmetric helium trimer
Aniket Bhattachatya and James B. Anderson
Department of Chemistry,The PennsylvaniaState University, University Park, Pennsylvania16802
(Received 11 January 1994; accepted 10 March 1994)
The interaction potential of three helium atoms in symmetric linear configurations is calculated
under the Born-Oppenheimer approximation using an "exact" Green's function quantum Monte
Carlo method. The results are compared with those of "exact" quantum Monte Carlo calculations
for the helium dimer and the Axih-od-Teller triple-dipole energy expression. For nearest neighbor
separations of 5.6 bohrs, the equilibrium distance for a helium dimer, the corresponding trimer
energy is -21.5% 1.9 K, compared to -22.3kO.2 K, calculated for pairwise additive behavior. For
all internuclear separations in the neighborhood of the van der Waals well (-5.6 bohrs), the
nonadditive contribution is found to be very small.
The interaction between two helium atoms has recently
been calculated accurately by analytic variational"2 as well
as "exact" Green's function Monte Carlo methods.3 The cal-
culated potentials are in good agreement with an experi-
mental-theoretical compromise potential" which is consis-
tent with many experimental measurements. For distances
close to the van der Waals minimum for the three helium
atoms, the interaction is generally expected to be very nearly
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